Tooth whitening oral care product with core shell silica particles

ABSTRACT

The present invention provides a tooth whitening oral care composition comprising: (i) a dye having a blue to blue-violet color with a hue angle in the CIELAB system ranging from 200 to 320 degrees; (ii) core shell silica particles, wherein each core shell silica particle comprises a silica core, and a surface of the silica core is etched with metal silicate; (iii) an orally acceptable carrier vehicle comprising a non-aqueous solvent; and wherein the composition comprises water in an amount of from 3 weight % to 30 weight %.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a U.S. national stage application under 35U.S.C. § 371 of PCT Application No. PCT/US2014/071511 filed Dec. 23,2013, that claims priority to U.S. Provisional Patent Application Ser.No. 61/918,938 filed 20 Dec. 2013 and U.S. Provisional PatentApplication Ser. No. 61/918,925, filed 20 Dec. 2013; and is acontinuation of International Application No. PCT/US2014/071298 filed 18Dec. 2014; International Application No. PCT/US2014/071304 filed 18 Dec.2014; and International Application No. PCT/US2014/071337 filed 19 Dec.2014, the entireties of which are incorporated herein by reference.

BACKGROUND

Many individuals are dissatisfied with their current tooth color. Thus,there is a desire for whiter teeth which can be achieved through the useof tooth whitening products. The whitening effect can be effected bychemically altering or removing the stain and/or changing the visualperception of the color of the teeth is known in the literature that thevisual perception of a white substance can be altered through thedeposition of an optical brightener, blue pigment or blue dye,especially one for which the hue angle (in the CIELAB scale) of thereflected or emitted light is between 200 to 320 degrees. This effect iscommonly used in laundry detergent products to make white clothes appear“whiter” to the human eye. The same concept has been applied to toothwhitening as well. The natural off-white or yellow color of teeth can bemade to appear whiter through the deposition of a blue substance ontoteeth. Using pigments with a deposition aid, such as Gantrez®(copolymers of maleic anhydride and with methyl vinylether) intoothpaste to make teeth look whiter is disclosed in EP1935395B1.

It has been demonstrated in EP1935395 that the deposition of the bluesubstance from aqueous solutions onto teeth is optimal if the bluesubstance has limited solubility in saliva as is the case with a bluepigment. In addition, it was shown that the deposition is optimal if ahigh molecular weight polymer (MW>200,000 Da) such as Gantrez typepolymers, PEGs, and cellulose ethers was present in the formulation tohelp the pigment adhere to the tooth. It is also known that otherpolymers, specifically low molecular weight hydroxypropylmethylcellulosepolymers, can increase the deposition of blue pigment on teethespecially when the blue pigment is encapsulated within the matrix of astrip of the polymer.

Dyes have significantly different properties than pigments, inparticular, dyes are much more soluble in water than pigments. Thissolubility of dyes makes them much more difficult to deposit and beretained on teeth. U.S. Pat. No. 6,030,222 discloses depositing dyes onteeth when blended with specific carriers. US Patent ApplicationPublication 2012/0093905 discloses dyes coupled to certain polymers.

Blue dye, such as FD&C blue #1 or FD&C blue #5, is of a differentchemical structure than blue pigment 15 so has a different solubility inwater. In fact, the solubility of FD&C Blue #1 dye is >20 g/100 mL inwater, as compared to <0.1 g/100 ml for blue pigment 15. The greatersolubility of blue dye in water as compared to blue pigment willlogically make it more difficult to deposit and retain blue dye on teethin the hydrated environment of the oral cavity. To increase thedeposition of blue dye Unilever has filed a patent application in whichthey covalently attach blue dye to a polymer backbone (US2012/0093905A1). Luster White Now markets a toothpaste which claims to instantlywhiten teeth in which a PVM/MA Copolymer is included in the formulationto presumably increase the retention of FD&C Blue #1 on teeth. Anothergranted patent (U.S. Pat. No. 6,030,222) claims to increasetooth-whitening through the absorption of blue dye into the pores ofteeth, preferable from a hydrophilic carrier which aids absorption ofthe complementary dyes into the aqueous environment surrounding theteeth.

It would be desirable to have tooth whitening oral care productscontaining dyes that can produce superior temporary tooth whiteningeffects when incorporated into oral care products.

BRIEF SUMMARY

In one aspect, the present invention provides a tooth whitening oralcare composition comprising:

-   -   (i) a dye having a blue to blue-violet color with a hue angle in        the CIELAB system ranging from 200 to 320 degrees;    -   (ii) core shell silica particles, wherein each core shell silica        particle comprises a silica core, and a surface of the silica        core is etched with metal silicate;    -   (iii) an orally acceptable carrier vehicle comprising a        non-aqueous solvent; and

wherein the composition comprises water in an amount of from 3 weight %to 30 weight %.

In a further aspect, the present invention provides a process for thepreparation of a composition as defined in any preceding claim, theprocess comprising:

-   -   i) admixing an amount of silica particles in water with an        amount of a base, the base comprising a metal ion, to produce        the core shell silica particles, wherein each core shell silica        particle comprises a silica core, and a surface of the silica        core is etched with metal silicate;    -   ii) admixing the core shell silica particles formed in step i)        with an orally acceptable carrier vehicle comprising a        non-aqueous solvent, a dye having a blue to blue-violet color        with a hue angle in the CIELAB system ranging from 200 to 320        degree, and an amount of water to produce a composition        comprising from 3 weight % to 30 weight % water.

In another aspect, the present invention provides a method for whiteningteeth comprising administering a composition according to the presentinvention to the oral cavity of a subject in need thereof.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the structure of an exemplary core shell silica particleaccording to some embodiments of the present invention.

FIG. 2 depicts the strucutre of an exemplary core shell silica particleaccording to further embodiments of the present invention.

DETAILED DESCRIPTION

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The present invention provides a tooth whitening oral care compositioncomprising:

-   -   (i) a dye having a blue to blue-violet color with a hue angle in        the CIELAB system ranging from 200 to 320 degrees;    -   (ii) core shell silica particles, wherein each core shell silica        particle comprises a silica core, and a surface of the silica        core is etched with metal silicate;    -   (iii) an orally acceptable carrier vehicle comprising a        non-aqueous solvent; and

wherein the composition comprises water in an amount of from 3 weight %to 30 weight %.

We have surprisingly found that when the surface chemistry of silica ismodified with a strong base the resulting particle can increase theretention of blue dye on the surface, providing a novel whitening agent.This novel material consisting of a silica core etched with silicate isreferred to as core shell silica (CSS). It is understood that in someembodiments the blue dye forms a non-covalent complex with the CSSparticles, in particular when the dye comprises a metal ion.

Dye

The dye should have a hue angle, h, in the CIELAB system of from 200 to320 degrees, more particularly between 250 and 290 degrees. The dye maybe a blue dye such as FD&C Blue#1, FD&C Blue #2, D&C Blue #4, CI FoodBlue 5, Acid Blue 1, or a mixture thereof. The dye may comprises amixture of one or more blue dyes and one or more red dyes.

A detailed description of hue angle may be found on p. 57 of ColorChemistry (Synthesis, Properties, and Applications of Organic Dyes andPigments), 3rd edition by H. Zollinger published by Wiley-VCH (2001).While the preferred single dyes are blue or violet, the same effect maybe achieved through mixing dyes outside of this h range; for example,such a hue angle may also be obtained by mixing a red and blue dye toyield a blue or blue-violet shaded dye. Typically, the dye is capable ofreflecting sufficient light such that the treated tooth is perceivablywhiter than its initial color. Preferably, the dye is colored such thatits natural color is within the violet-red to green-blue color,typically from violet to blue.

Preferred dyes are water soluble dyes. The term “water-soluble” in thisparticular context generally means that the dye has an aqueoussolubility of at least 10 g/L at 25° C., most preferably at least 100g/L at 25° C. (where the solubility is determined in un-buffereddistilled water). Triarylmethane dyes are examples of water soluble dyesuseful in the present invention. In some embodiments, dyes useful hereinare anionic triphenylmethane dyes, and especiallydiaminotriphenylmethane dyes containing from two to four sulphonategroups, such as those corresponding to general formula (I):

in which R₁, R₂, R₃ and R₄ are monovalent moieties which are eachindependently selected from hydrogen (—H), hydroxyl (—OH), halo (e.g.—Cl) and sulphonate (—SO₃ ⁻) groups, with the proviso that at least twoof R₁ to R₁ are sulphonate groups.

An example of a dye useful herein is FD&C Blue #1, also known asBrilliant Blue FCF (Blue 1) as well as other commercial names, whichcorresponds to general formula (I), wherein R₂ is —H and R₁, R₃, and R₄are sulphonate groups. FD&C Blue #1 (CAS No. [3844-45-9]) is a colorantfor foods and other substances to induce a color change. It is denotedby E number E133 and has a color index of 42090 (CI 42090). It has theappearance of a reddish-blue powder. It is soluble in water, and thesolution has a maximum absorption at about 628 nanometer. It is asynthetic dye produced using aromatic hydrocarbons from petroleum. It isusually a disodium salt. The diammonium salt (D&C Blue #4) has CAS No.[2650-18-2]. Calcium and potassium salts are also known. Other dyesuseful herein are FD&C Blue #2 (Indigo Carmine, CI 73015, CAS No.[860-22-0]), CI Food Blue 5 (CI 42051; also known as Acid Blue 3, CASNo. [3536-49-0]), Acid Blue 1 (CI 42045, CAS No. [129-17-9]) and thelike. In some embodiments, the dye is FD&C Blue#1, FD&C Blue #2, D&CBlue #4, CI Food Blue 5, Acid Blue 1, or a mixture thereof.

Mixtures of dyes also can be used even if an individual dye has a hueangle outside the desired range as long as the mixture of dyes will bewithin the range. For example, red dyes, e.g., FD&C Red #3, FD&C Red#40, and the like, can be used. In one embodiment FD&C Blue #1 is usedin combination with FD&C Red#40.

Delta b* is a magnitude of color change along a yellow-blue axis,negative delta b* corresponding to reduced yellowness.

The amount of dye in the oral care composition can be from 0.001 to 2weight %, from 0.002 to 1.5 weight %, from 0.003 to 1.25 weight %, from0.004 to 1 weight %, from 0.005 to 0.5 weight %, from 0.0075 to 0.25weight %, from 0.01 to 0.1 weight %, from 0.02 to 0.07 weight %, or from0.03 to 0.05 weight %. In some embodiments, the amount of dye in theoral care composition is about 0.03 weight %. In some embodiments, theamount of dye in the oral care composition is about 0.05 weight %. Thedye may be uniformly spread throughout the composition or, it may bedispersed in a second phase such as a stripe or other coextruded secondphase. Such “dual phase” compositions have the advantage that the phasesmay be differently colored, presenting a more visually attractiveproduct to the consumer.

In some embodiments a blue pigment may be used instead of a dye.

In some embodiments, the composition is free from peroxide whiteningagents. By “free from peroxide whitening agents”, it is meant that thecomposition contains less than 0.1 weight %, less than 0.05 weight %, orless than 0.01 weight % peroxide whitening agents; or substantially noperoxide whitening agents; or that the composition contains no peroxidewhitening agents. The tooth whitening effect of the oral carecompositions of the present invention is provided by the presence of thedye, rather than by the presence of any peroxide whitening agents.

Description of the Core Shell Silica Particles

Core shell silica particles are prepared by etching silica (SiO₂) with abase to form core(Silica)-shell(metal silicate) structured colloids. Forexample using NaOH as the base, core(SiO₂)-shell(Na₂SiO₃) structuredcolloids are formed. The reaction is as follows:

The Na₂SiO₃ molecules contribute 2 negative charges with 2 Na+ counterions on the colloidal core-shell silica particle surface.

A surface of the silica core is etched with metal silicate. The term“etched” means that a surface of the silica core is dissolved, and metalsilicate is formed on top of the silica core. The process for making thecore shell silica particles comprises etching the original silica inorder to form the metal silicate, such as Na₂SiO₃. The reaction of thesilica particle with base causes a reduction in the diameter of thesilica particle to form a silica core, and metal silicate is formed ontop of the silica core. The Na₂SiO₃ layers are not additional layerscoated on top of the original surface of the silica.

Typically the metal silicate is:

i. a metal silicate of a monovalent metal ion; or

ii. a metal silicate of; a monovalent metal ion and one or more of a ofa divalent metal ion, a trivalent metal ion, and a tetravalent metalion.

The metal silicate optionally comprises the formula M¹ ₂SiO₃.x H₂O,wherein M is a group I metal, and x is from 0 to 10. The metal silicatemay be anhydrous, i.e. x=0, or may be hydrated. Preferably, M is Na orK.

The surface of the silica core may be the outer surface of the silicacore (see FIG. 1).

Alternatively, or in addition, the surface of the silica core may be aninternal surface of the silica core (see FIG. 2).

In one embodiment the outer 10 nm depth of each particle comprises from0.1 to 10, optionally 0.1 to 2 weight % M¹ ₂SiO3.xH₂O.

In one embodiment the outer 10 nm depth of each particle has the generalformula:(SiO₂)_(p)[O_(o)*N⁺ _(n)H⁺ _(h)OH⁻ _(j) ].qH₂Owherein O* is oxygen in the silicate form; M is a group I metal ion; p,o, n, h, j and q are the atomic percentages of each component (p is theatomic percentage of SiO₂, O is the atomic percentage of oxygen in thesilicate form, m is the atomic percentage of group I metal, h is theatomic percentage of H⁺, j is the atomic percentage of OH⁻, and q is theatomic percentage of H₂O); and the total charge of each core shellsilica particle is zero.

Typically the atomic percentage for each component except H+ isdetermined by electron spectroscopy for chemical analysis (ESCA).

Optionally, the outer 10 nm depth of each particle has one of thefollowing compositions:(SiO₂)_(30.30)Na_(0.41).8.70H₂O(SiO₂)_(30.67)Na₆₇Na_(0.36).7.63H₂O(SiO₂)_(23.25)[O*_(11.73)H_(10.26)Na_(13.20)].5.33H₂O

In one embodiment the metal silicate is a silicate of a monovalent metalion and one or more of a divalent metal ion, a trivalent metal ion, anda tetravalent metal ion. These types of CSS particles are typicallyformed when the monovalent ions are displaced by divalent and/ortrivalent and/or tetravalent ions.

Typically, the metal silicate comprises a silicate of a group 2 metalion, a transition metal ion, a group 13 metal ion, a group 14 metal ionor mixtures thereof. Optionally, the metal silicate comprises a silicateof Ca²⁺, Mg²⁺, Zn²⁺, Sn²⁺, Sr²⁺, Al³⁺, Zr⁴⁺, Ti⁴⁺, Fe³⁺, Fe²⁺, Mo²⁺,Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Pd²⁺, Mo²⁺, Ru²⁺ or mixtures thereof.

Optionally the metal silicate comprises the formula M²SiO₃.x H₂O,wherein M² is a divalent metal ion, and x is from 0 to 10. M² may beselected from the group consisting of Zn, Ca, Mg, Sn, and Sr, optionallywherein M² is Zn.

In another embodiment, each core shell silica particle comprises asilica core, and a surface of the silica core etched with metalsilicate, the core shell silica particles prepared by:

-   -   i) admixing an amount of silica particles in water with an        amount of a base, wherein the base comprises a monovalent metal        ion, to produce core shell silica particles, each core shell        silica particle comprising a silica core, and a surface of the        silica core etched with a silicate of the monovalent metal ion;        and    -   ii) reacting the core shell silica particles formed in step i)        with a metal salt comprising a second metal ion, to form core        shell silica particles comprising silicate of the second metal        ion on the surface of the silica core.

It will be understood that the second metal ion typically displaces themonovalent metal ion from the metal silicate on the surface of thesilica core. There may be from 5-95 weight % of the monovalent metal iondisplaced by the second metal ion, optionally 25 to 65 weight %. Theamount of monovalent metal ion displaced by the second metal ion may be1, 2, 5, 10, 15, 20, 30, 40, 50, 60, 70, or 80 weight %.

In a preferred embodiment the monovalent metal ion is a group 1 metalion. Particularly preferred as the monovalent metal ion is a sodium ionor potassium ion.

The base is not especially limited, provided it comprises the monovalentmetal ion. The base is typically a strong base. The base may be selectedfrom the group consisting of sodium hydroxide, potassium hydroxide,sodium carbonate, potassium carbonate, trisodium phosphate, disodiumphosphate, potassium phosphate, dipotassium phosphate, tetrasodiumpyrophosphate, and tetrapotassium pyrophosphate. Sodium or potassiumhydroxide are preferred bases. The base may have a pKb value in therange 0.1 to 3. For example sodium hydroxide has a pKb of 0.2, andpotassium hydroxide has a pKb of 0.5.

The second metal ion is not especially limited provided it can displacethe monovalent metal ion from the silicate of the monovalent metal ion.The second metal ion may be a divalent metal ion, a trivalent metal ion,a tetravalent metal ion or mixtures thereof. Most preferably the secondmetal ion is a divalent metal ion. The second metal ion may be a group 2metal ion, a transition metal ion, a group 13 metal ion, a group 14metal ion or mixtures thereof. Preferably the second metal ion is Ca²⁺,Mg²⁺, Zn²⁺, Sn²⁺, Sr²⁺, Al³⁺, Zr⁴⁺, Ti⁴⁺, Fe³⁺, Fe²⁺, Mo²⁺, Co²⁺, Ni²⁺,Mn²⁺, Cu²⁺, Pd²⁺, Mo²⁺, Ru²⁺ or mixtures thereof. In a particularlypreferred embodiment the second metal ion is Zn²⁺.

By changing the first and second metal ions, core shell silica particleswith different utilities can be provided. For example Zn—CSS are usefulas antibacterial agents and anti-malodor agents, with a taste profilewhich is better than the taste profile of zinc salts such as ZnCl₂. TheCSS particles retain their antibacterial and/or antimalor propertieswhen in the dye composition. For example, blue toothpaste was preparedusing blue #1 dye and it reduced malodor/or kill bacteria in saliva withthe same efficacy as Total toothpaste.

The silicates may be hydrated or anhydrous.

It will be understood that the ability of ions of the metal silicate onan internal or outer surface of the CSS particles to be displaced isalso behind the utility of the CSS particles as anti-tartar agents. Freecalcium ions in saliva displace the monovalent metal ions and/or thesecond metal ions of the CSS particles, leading to a reduction in theconcentration of calcium ions in saliva. This leads to a reduction inthe formation of Ca₃(PO₄)₂, the main constituent of tartar. CSSparticles with a higher weight % of metal silicate are better tartarcontrol agents because they contain more sites available for calcium ionchelation.

In one embodiment the silicate of the monovalent metal ion formed instep i) comprises the formula M¹ ₂:SiO₃.x H₂O, wherein M¹ is amonovalent metal ion, optionally a group I metal ion, and x is from 0 to10. M¹ is preferably Na⁺ or K⁺.

The silicate of the second metal ion formed in step ii) typicallycomprises the formula M²SiO₃.x H₂O, wherein M² is a divalent metal ion,and x is from 0 to 10. M² is preferably selected from the groupconsisting of Zn²⁺, Ca²⁺, Mg²⁺, Sn²⁺, and Sr²⁺.

The metal salt may be selected from the group consisting of a metalacetate, metal borate, metal butyrate, metal carbonate, metal halide,metal citrate, metal formate, metal gluconate, metal glycerate, metalglycolate, metal lactate, metal oxide, metal phosphate, metalpicolinate, metal proprionate, metal salicylate, metal silicate, metalstearate, metal tartrate, metal undecylenate and mixtures thereof. In apreferred embodiment the metal salt is a metal halide. Most preferably,the metal halide is a metal chloride. Examples are ZnCl₂, SnCl₂, SrCl₂,AlCl₃, FeCl₃, TiCl₄, and ZrCl₄. In a particularly preferred embodimentthe metal salt is a zinc salt. The metal salt may be a zinc saltselected from the group consisting of zinc acetate, zinc borate, zincbutyrate, zinc carbonate, zinc chloride, zinc citrate, zinc formate,zinc gluconate, zinc glycerate, zinc glycolate, zinc lactate, zincoxide, zinc phosphate, zinc picolinate, zinc proprionate, zincsalicylate, zinc silicate, zinc stearate, zinc tartrate, zincundecylenate and mixtures thereof. The most preferred zinc salt is zincchloride.

In a preferred embodiment the silicate of the second metal ion comprisesZnSiO₃.xH₂O, wherein x is from 0 to 10.

In one embodiment the surface of the silica core is the outer surface ofthe silica core. In addition or as an alternative the surface of thesilica core may be an internal surface of the silica core.

The silicate of the second metal ion may comprise at least 5 weight %,10 weight %, 20 weight %, 30 weight %, 40 weight %, 50 weight %, 60weight %, or 95 weight % of the total metal silicate of the CSSparticles.

The outer 10 nm depth of each particle may comprise from 0.1 to 10weight % metal silicate. In one embodiment the outer 10 nm depth of eachparticle has the general formula:(SiO₂)_(p)[O*_(o)N⁺ _(n)M²⁺ _(m)U³⁺ _(n)V⁴⁺ _(v)H⁺ _(h)OH⁻ _(j) ].qH₂Owherein O* is oxygen in the silicate form; N is a monovalent metal ion;M is a divalent metal ion; U is a trivalent metal ion; V is atetravalent metal ion; p, o, n, m, u, v, h, j and q are the atomicpercentages of each component; and the total charge of each core shellsilica panicle is zero.

The atomic percentage for each component except H+ is typicallydetermined by electron spectroscopy for chemical analysis (ESCA). In oneexample, using ESCA data, the following elements were detected:O_(56.81)Si_(26.52)O*_(7.35)Na_(3.18)Zn_(4.65)Cl_(1.49)By setting the total electric charge to zero by adding H+ and water, weconclude that in one embodiment the outer 10 nm depth of each particlemay have the following composition:(SiO₂)_(26.52)[O*_(7.35)Na_(3.18)Zn_(4.65)Cl_(1.49)H_(3.73)].3.77H₂O

In one embodiment, the core shell silica particles comprise up to 20weight % total metal.

In one embodiment, the d(0.5) value of the particles is from 5 nm to 50μm.

The d(0.5) value of the particles may be from 26 μm to 40 μm. Particleshaving a d(0.5) value within this range are typically translucent.Translucent particles are those which allow light to pass through,although it is not possible to see an image through the particles. Thisis distinguished from transparent compositions which allow light to passthrough and an image can be seen through the composition. Methods fordetermine particle size are well known in the art. For example particlesize may be determined using light scattering methodologies, such asusing the Mastersizer 2000, Hydro 2000S, Malvern Instruments Limited.

The d(0.5) value of the particles may be from 18 μm to 25 μm. The d(0.5)value of the particles may be from 10 μm to 15 μm. The d(0.5) value ofthe particles may be from 5 nm to 12 nm.

The d(0.5) or d50 of the particles is the diameter (typically inmicrons) that splits the distribution with half the population above andhalf below this diameter. It will be noted that this parameter is avalue for a population of particles, and that the diameter of anindividual particle may be larger or smaller than the d(0.5) valuesdescribed herein. The Dv50 (or Dv0.5) is the median for a volumedistribution, Dn50 is used for number distributions, and Ds50 is usedfor surface distributions. In the present context, d(0.5) will be usedto refer to the median particle size for a volume distribution.

The d(0.1) value of the particles is the diameter that splits thedistribution with 10% of the population below and 90% above thisdiameter.

The d(0.9) value of the particles is the diameter that splits thedistribution with 90% of the population below and 10% above thisdiameter.

A value used to describe the distribution width of the particle sizedistribution is the span:Span=(d(0.9)−d(0.1))/d(0.5)

The span of the core shell silica particles according to the presentinvention is typically from 1.5 to 3.

In a preferred embodiment, the CSS have a d(0.1) of from 10 to 13 μm, ad(0.5) of from 30 to 33 μm, and a d(0.9) of from 61 to 64 μm.

In another preferred embodiment, the CSS have a d(0.1) of from 6 to 9μm, a d(0.5) of from 18 to 21 μm, and a d(0.9) of from 41 to 45 μm.

In a further preferred embodiment, the CSS have a d(0.1) of from 3 to 5μm, a d(0.5) of from 11 to 14 μm, and a d(0.9) of from 33 to 36 μm.

In preferred embodiments, the d(0.5) value of the CSS particles is lessthan the mean diameter of a human dentin tubule. This allows the CSSparticles to enter the dentin tubules, which may be exposed on damage tothe protective enamel layer. In human teeth, dentin tubules taper fromthe inner to the outermost surface, and have a mean diameter of 2.5 μmnear the pulp, 1.2 μm in the middle of the dentin, and 0.9 μm at thedentino-enamel junction (seehttp://www.slideshare.net/DrAbusaliamah/history-of-dentin). Thus thed(0.5) value of the CSS particles is preferably less than 0.9 μm. In aparticularly preferred embodiment the d(0.5) value of the CSS particlesis less than the mean diameter of a human enamel tubule. Enamel tubulestypically have a mean diameter of from 50 to 100 nm. Thus the d(0.5)value of the CSS particles is preferably from 5 to 20 nm, optionally 5to 12 nm. Preferably, when the CSS particles are intended to enter theenamel tubules, these particles are prepared from fined silica. Fumedsilica consists of particles having a d(0.5) in the range of from 5 to20 nm which agglomerate into larger particles having a d(0.5) in themicrometer range.

CSS particles may be spherical, or substantially spherical however itwill be understood that the particles may have other shapes, for examplerod, needle, or ellipsoidal shapes. The particles may have irregularshapes. The particles may also form larger size aggregates.

The metal silicate may comprise a plurality of monolayers ofM₂SiO₃.xH₂O. The number of monolayers may be from 2 to 100, from 2 to40, 2 to 12 or 12 to 40 monolayers.

The particle may comprise 2, 4, 16, 32 or 36 surface metal silicatemonolayers.

The silica is preferably selected from the group consisting of aprecipitated silica, a fumed silica and a fused silica.

Core shell silica particles preferably have a high surface chargedensity and ion exchange capacity. Optionally, the core shell silicaparticles have a total cationic exchange capacity of from 0.5 to 5.0meq/g. Core shell silica particles with a high cationic exchangecapacity are particularly preferred, since this enables the CSS toexchange metal ions such as Na+ on their surface for calcium ions insaliva, inhibiting the formation of tartar.

In one embodiment, the core shell silica particles have a turbidity offrom 0.0 to 0.2 at a wavelength of from 300 to 800 nm using a 0.20 mmquartz UV optical cell. These particles may be described as translucentor transparent.

In another embodiment, the core shell silica particles have a turbidityof from 0.8 to 1.6 at a wavelength of from 300 to 800 nm using a 0.20 mmquartz UV optical cell. These particles may be described as semi-opaque.

In a further embodiment, the core shell silica particles have aturbidity of from 1.8 to 2.4 at a wavelength of from 300 to 800 nm usinga 0.20 mm quartz UV optical cell. These particles may be described asopaque.

In preferred embodiments, the amount of core shell silica particles is0.001 to 10 weight %, or 0.01 to 5 weight %, or 0.05 to 5 weight %, or0.1 to 5 weight %, or 0.5 to 5 weight %, or 0.5 to 3 weight %, or 1 to 2weight %, or about 1 weight % of the composition.

Orally Acceptable Carrier Vehicle

The oral care compositions of the invention include a vehicle or baseinto which the dye and core shell silica particles are incorporated. Thecarrier vehicle may be present in an amount of from 40 to 99 weight % orfrom 55 to 85 weight %, based on the total weight of the composition. Ithas been surprisingly discovered that when the dye is incorporated intoa non-aqueous carrier containing little or substantially no water, thetooth whiteness effect is enhanced. In some embodiments the orallyacceptable carrier vehicles comprises alcohols, polyhydric alcohols suchas glycerol, sorbitol, xylitol, propylene glycol, polyols, ketones,aldehydes, carboxylic acids or salts thereof, amines, or mixturesthereof. In one embodiment the carrier comprises glycerol. Suchmaterials typically also function as humectants.

In some aspects of the present invention, low amounts of water arepresent, e.g., from 3 weight % to 30 weight %, 5 to 17 weight %, 10 to17 weight %, 5 to 15 weight %, 5 weight % to less than 10 weight %, 5 to7 weight %, or about 7 weight %, about 10 weight %, or about 15 weight%.

It is surprising that the low water content of the compositions of theinvention allows for enhanced delivery of the dye to the teeth, sincethe dyes are water soluble. It is not desired to be bound by anyparticular theory or mechanism, but it is believed that use of thecompositions of the invention, with little or no water, drives the dyeinto the aqueous voids of the tooth enamel.

The orally acceptable carrier vehicle optionally can include variousother ingredients which are typically incorporated into dentifrices.Examples of such other ingredients include carrier polymers, humectants,abrasives, thickener silicas or any combination of two or more thereof.The term “orally-acceptable” refers to a material or ingredient whichcan be applied to the oral cavity in a safe manner during normal use.

Carrier Polymers

Carrier polymers can comprise one or more anionic or nonionic polymers,and also may include additional polymers to adjust the viscosity of theformulation or enhance the solubility of other ingredients.

Suitable carrier polymers include polyethylene glycols, polysaccharides(e.g., cellulose derivatives, for example carboxymethyl cellulose, orpolysaccharide gums, for example xanthan gum or carrageenan gum). Acidicpolymers, for example polyacrylate gels, may be provided in the form oftheir free acids or partially or fully neutralized water soluble alkalimetal (e.g., potassium and sodium) or ammonium salts. Anionic polymersmay be present in an amount of from about 0.001 to about 5%, moreparticularly about 0.01 to 5%, more particularly about 0.05 to 4%, moreparticularly about 0.05 to 3% of the composition. Examples of suchagents are disclosed in U.S. Pat. Nos. 5,188,821 and 5,192,531; andinclude synthetic anionic polymeric polycarboxylates, such as 1:4 to 4:1copolymers of maleic anhydride or acid with another polymerizableethylenically unsaturated monomer, preferably methyl vinyl etherimaleicanhydride having a molecular weight (M.W.) of about 30,000 to about1,000,000, most preferably about 300,000 to about 800,000. Thesecopolymers are available for example as Gantrez). e.g., AN 139 (M.W.500,000), AN 119 (M.W. 250,000) and preferably S-97 Pharmaceutical Grade(M.W. 700,000) available from ISP Technologies, Inc., Bound Brook, N.J.08805. Other operative polymers include those such as the 1:1 copolymersof maleic anhydride with ethyl acrylate, hydroxyethyl methacrylate,N-vinyl-2-pyrollidone, or ethylene, the latter being available forexample as Monsanto EMA No. 1103, M.W. 10,000 and EMA Grade 61, and 1:1copolymers of acrylic acid with methyl or hydroxyethyl methacrylate,methyl or ethyl acrylate, isobutyl vinyl ether or N-vinyl-2-pyrrolidone.Suitable generally, are polymerized olefinically or ethylenicallyunsaturated carboxylic acids containing an activated carbon-to-carbonolefinic double bond and at least one carboxyl group, that is, an acidcontaining an olefinic double bond which readily functions inpolymerization because of its presence in the monomer molecule either inthe alpha-beta position with respect to a carboxyl group or as part of aterminal methylene grouping. Illustrative of such acids are acrylic,methacrylic, ethacrylic, alpha-chloroacrylic, crotonic, beta-acryloxypropionic, sorbic, alpha-chlorsorbic, cinnamic, beta-styrylacrylic,muconic, itaconic, citraconic, mesaconic, glutaconic, aconitic,alpha-phenylacrylic, 2-benzyl acrylic, 2-cyclohexylacrylic, angelic,umbellic, fumaric, maleic acids and anhydrides. Other different olefinicmonomers copolymerizable with such carboxylic monomers includevinylacetate, vinyl chloride, dimethyl maleate and the like. Copolymerscontain sufficient carboxylic salt groups for water-solubility. Afurther class of polymeric agents includes a composition containinghomopolymers of substituted acrylamides and/or homopolymers ofunsaturated sulfonic acids and salts thereof, in particular wherepolymers are based on unsaturated sulfonic acids selected fromacrylamidoalykane sulfonic acids such as 2-acrylamide 2 methylpropanesulfonic acid having a molecular weight of about 1,000 to about2,000,000, described in U.S. Pat. No. 4,842,847, Jun. 27, 1989 to Zahid,incorporated herein by reference. Another useful class of polymericagents includes polyamino acids containing proportions of anionicsurface-active amino acids such as aspartic acid, glutamic acid andphosphoserine, (in addition to the basic amino acid polymers), e.g. asdisclosed in U.S. Pat. No. 4,866,161 Sikes et al., incorporated hereinby reference.

In preparing oral care compositions, it is sometimes necessary to addsome thickening material to provide a desirable consistency or tostabilize or enhance the performance of the formulation. In certainembodiments, the thickening agents are carboxyvinyl polymers,carrageenan, hydroxyethyl cellulose and water soluble salts of celluloseethers such as sodium carboxymethyl cellulose and sodium carboxymethylhydroxyethyl cellulose. Hydroxyalkyl methyl cellulose may also bepresent in the oral composition. Natural gums such as karaya, gumarabic, and gum tragacanth can also be incorporated. Colloidal magnesiumaluminum silicate or finely divided silica can be used as component ofthe thickening composition to further improve the composition's texture.In certain embodiments, thickening agents in an amount of about 0.05% to5 weight %, more particularly about 0.5 to 5 weight % of the totalcomposition are used. Orally acceptable carrier polymers for use in theinvention are typically water soluble. Suitable orally acceptablecarrier polymers for use in the invention will generally dissolve ordisperse in water at a temperature of 25° C.

The amount of orally acceptable carrier vehicle polymer in compositionsof the invention, whether enhancers, deposition aids, thickeners or thelike, or of a combination thereof, suitably ranges from about 0.001 to10 weight %, more particularly about 0.005 to 5 weight %, moreparticularly about 1 to 5 weight %, and more particularly about 1 to 3weight %.

The composition may further comprise an additional agent selected fromfluoride, arginine in free or orally acceptable salt form, anantibacterial agent, an anti-inflammatory agent, and a combination oftwo or more thereof.

The composition may be in the form of a dentifrice.

In one embodiment the composition is a toothpaste comprising one or moreof an abrasive, a surfactant, a foaming agent, a vitamin, a polymer, anenzyme, a humectant, a thickener, an antimicrobial agent, apreservative, a flavoring, and/or a combination of two or more thereof.

The composition may be free from peroxide whitening agents.

Humectants

Within certain embodiments of the oral compositions, it is alsodesirable to incorporate a humectant to prevent the composition fromhardening upon exposure to air. Certain humectants can also impartdesirable sweetness or flavor to dentifrice compositions. The humectant,on a pure humectant basis, generally includes about 15% to about 70weight % in one embodiment or about 30% to about 65 weight % in anotherembodiment by weight of the dentifrice composition. Suitable humectantsinclude edible polyhydric alcohols such as glycerine, sorbitol, xylitol,propylene glycol as well as other polyols and mixtures of thesehumectants. Mixtures of glycerine and sorbitol may be used in certainembodiments as the humectant component of the toothpaste compositionsherein.

Abrasives

The compositions of the invention may comprise a calcium phosphateabrasive, e.g., tricalcium phosphate (Ca₃(PO₄)₂), hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂), or dicalcium phosphate dihydrate (CaHPO₄.2H₂O, alsosometimes referred to herein as DiCal) or calcium pyrophosphate. Thecompositions may include one or more additional abrasives, for examplesilica abrasives such as precipitated silicas having a mean particlesize of up to about 20 microns, such as Zeodent 115®, marketed by J. M.Huber. Other useful abrasives also include sodium metaphosphate,potassium metaphosphate, aluminum silicate, calcined alumina, bentoniteor other siliceous materials, or combinations thereof. The silicaabrasive polishing materials useful herein, as well as the otherabrasives, generally have an average particle size ranging between about0.1 and about 30 microns, about between 5 and about 15 microns. Thesilica abrasives can be from precipitated silica or silica gels, such asthe silica xerogels described in U.S. Pat. No. 3,538,230, to Pader etal. and U.S. Pat. No. 3,862,307, to Digiulio, both incorporated hereinby reference. Particular silica xerogels are marketed under the tradename Syloid® by the W. R. Grace & Co., Davison Chemical Division. Theprecipitated silica materials include those marketed by the J. M. HuberCorp. under the trade name Zeodent®, including the silica carrying thedesignation Zeodent 115 and 119. These silica abrasives are described inU.S. Pat. No. 4,340,583, to Wason, incorporated herein by reference. Incertain embodiments, abrasive materials useful in the practice of theoral care compositions in accordance with the invention include silicagels and precipitated amorphous silica having an oil absorption value ofless than about 100 cc/100 g silica and in the range of about 45 cc/100g to about 70 cc/100 g silica. Oil absorption values are measured usingthe ASTA Rub-Out Method D281. In certain embodiments, the silicas arecolloidal particles having an average particle size (d(0.5)) of about 3microns to about 12 microns, and about 5 to about 10 microns. Low oilabsorption silica abrasives particularly useful in the practice of theinvention are marketed under the trade designation Sylodent XWA® byDavison Chemical Division of W.R. Grace & Co., Baltimore, Md. 21203.Sylodent 650 XWA®, a silica hydrogel composed of particles of colloidalsilica having a water content of 29% by weight averaging about 7 toabout 10 microns in diameter, and an oil absorption of less than about70 cc/100 g of silica is an example of a low oil absorption silicaabrasive useful in the practice of the present invention. The abrasivemay be present in the oral care composition of the present invention ata concentration of about 10 to about 60% by weight, in other embodimentabout 20 to about 45% by weight, and in another embodiment about 30 toabout 50% by weight.

Product Form

Examples of suitable product forms for compositions of the inventioninclude dentifrices. The term “dentifrice” generally denotesformulations which are used to clean the surfaces of the oral cavity.The dentifrice is an oral composition that is not intentionallyswallowed for purposes of systemic administration of therapeutic agents,but is applied to the oral cavity, used to treat the oral cavity andthen expectorated. Typically the dentifrice is used in conjunction witha cleaning implement such as a toothbrush, usually by applying it to thebristles of the toothbrush and then brushing the accessible surfaces ofthe oral cavity. Preferably the dentifrice is in the form of a paste ora gel (or a combination thereof).

Active Agents

The effective concentration of the active ingredients for optional useherein will depend on the particular agent and the delivery system used.It is understood that a toothpaste for example will typically be dilutedwith water upon use, while a mouth rinse typically will not be. Thus, aneffective concentration of active in a toothpaste will ordinarily be5-15× higher than required for a mouth rinse. The concentration willalso depend on the exact salt or polymer selected. For example, wherethe active agent is provided in salt form, the counterion will affectthe weight of the salt, so that if the counterion is heavier, more saltby weight will be required to provide the same concentration of activeion in the final product. Active agents can include one or more of afluoride ion source, an anti-calculus agent, an amino acid, anantibacterial agent, and the like.

Arginine, where present, may be present at levels from about 1 to about10 weight % for a consumer toothpaste or about 7 to about 20 weight %for a professional or prescription treatment product.

Fluoride where present may be present at levels of between about 25 ppmto about 25,000 ppm of fluoride ions. For consumer toothpastes, thefluoride level may be between about 500 to about 1600 ppm, or betweenabout 500 to about 1000 ppm, or between about 1000 to about 1600 ppm,e.g., about 1100 ppm or 1450 ppm. The appropriate level of fluoride willdepend on the particular application. A dentifrice or coating forprofessional application could have as much as about 5,000 or even about25,000 ppm fluoride, e.g. a range of about 3,000 ppm to about 8,000 ppmfluoride.

Antibacterial agents may be included in the oral composition of thepresent invention and particularly noncationic halogenated diphenylethers agents which are desirable from considerations of effectivenessand safety, such as 2′,4,4′ trichloro-2 hydroxy-diphenyl ether(Triclosan) and 2,2′-dihydroxy-5,5′ dibromophenyl ether. Otherantibacterial agents, e.g. zinc salts, may be included in thecompositions of the present invention. The antibacterial agent, whenpresent in the oral composition, is present in concentrations of about0.05 to about 2% by weight and preferably 0.1 to about 1% by weight. Forexample, a triclosan toothpaste may contain about 0.3 weight %triclosan.

Agents used to diminish teeth sensitivity such as potassium chloride,potassium nitrate, potassium citrate, dipotassium oxalate, or zincphosphate may also be included in oral compositions of the presentinvention at concentrations of about 0.1 to about 10% by weight.

Fluoride Ion Source

The oral care compositions may further include one or more fluoride ionsources, e.g., soluble fluoride salts. A wide variety of fluorideion-yielding materials can be employed as sources of soluble fluoride inthe present compositions. Examples of suitable fluoride ion-yieldingmaterials are found in U.S. Pat. No. 3,535,421, to Briner et al.; U.S.Pat. No. 4,885,155, to Parran, Jr. et al. and U.S. Pat. No. 3,678,154,to Widder et al., incorporated herein by reference. Representativefluoride ion sources include, but are not limited to, stannous fluoride,sodium fluoride, potassium fluoride, sodium monofluorophosphate, sodiumfluorosilicate, ammonium fluorosilicate, amine fluoride, ammoniumfluoride, and combinations thereof. In certain embodiments the fluorideion source includes stannous fluoride, sodium fluoride, sodiummonofluorophosphate as well as mixtures thereof. In certain embodiments,the oral care composition of the invention may also contain a source offluoride ions or fluorine-providing ingredient in amounts sufficient tosupply about 25 ppm to about 25,000 ppm of fluoride ions, generally atleast about 500 ppm, e.g., about 500 to about 1000 ppm, e.g., about 1000to about 1600 ppm, e.g., about 1100 ppm or 1450 ppm. The appropriatelevel of fluoride will depend on the particular application. Atoothpaste for general consumer use would typically have about 1000 toabout 1500 ppm, with pediatric toothpaste having somewhat less. Adentifrice or coating for professional application could have as much asabout 5,000 or even about 25,000 ppm fluoride, e.g. a range of about3,000 ppm to about 8,000 ppm fluoride.

Fluoride ion sources may be added to the compositions of the inventionat a level of about 0.01 weight. % to about 10 weight. % in oneembodiment or about 0.03 weight. % to about 5 weight. %, and in anotherembodiment about 0.1 weight. % to about 1 weight. % by weight of thecomposition in another embodiment. Weights of fluoride salts to providethe appropriate level of fluoride ion will obviously vary based on theweight of the counter ion in the salt.

Foaming Agents

The oral care compositions of the invention also may include an agent toincrease the amount of foam that is produced when the oral cavity isbrushed. Illustrative examples of agents that increase the amount offoam include, but are not limited to polyoxyethylene and certainpolymers including, but not limited to, alginate polymers. Thepolyoxyethylene may increase the amount of foam and the thickness of thefoam generated by the oral care carrier component of the presentinvention. Polyoxyethylene is also commonly known as polyethylene glycol(“PEG”) or polyethylene oxide. The polyoxyethylenes suitable for thisinvention will have a molecular weight of about 200,000 to about7,000,000. In one embodiment the molecular weight will be about 600,000to about 2,000,000 and in another embodiment about 800,000 to about1,000,000. Polyox® is the trade name for the high molecular weightpolyoxyethylene produced by Union Carbide. The polyoxyethylene may bepresent in an amount of about 1% to about 90%, in one embodiment about5% to about 50% and in another embodiment about 10% to about 20% byweight of the oral care carrier component of the oral care compositionsof the present invention. The dosage of foaming agent in the oral carecomposition (i.e., a single dose) may be about 0.01 to about 0.9% byweight, about 0.05 to about 0.5% by weight, and in another embodimentabout 0.1 to about 0.2% by weight.

Anticalculus Agents

The oral composition can include at least one anti-calculus composition,such as one or more of the anti-calculus compositions recited in U.S.Pat. No. 5,292,526 titled “Antibacterial Anti-plaque Anticalculus OralComposition,” which is incorporated herein by reference. In variousembodiments, the anti-calculus composition includes one or morepolyphosphates. The anti-calculus composition can include at least onewholly or partially neutralized alkali metal or ammoniumtripolyphosphate or hexametaphosphate salt present in the oralcomposition at an effective anti-calculus amount. The anti-calculuscomposition can also include at least one water soluble, linear,molecularly dehydrated polyphosphate salt effective in an anticalculusamount. The anti-calculus composition can also include a mixture ofpotassium and sodium salts at least one of which is present in aneffective anti-calculus amount as a polyphosphate anti-calculus agent.The anti-calculus composition can also contain an effective anticalculusamount of linear molecularly dehydrated polyphosphate salt anti-calculusagent present in a mixture of sodium and potassium salts. Other usefulanticalculus agents include polycarboxylate polymers and polyvinylmethyl ether/maleic anhydride (PVME/MA) copolymers, such as GANTREZ®

Surfactants

The compositions useful in the invention may contain anionic and/ornonionic surfactants, for example:

i. water-soluble salts of higher fatty acid monoglyceride monosulfates,such as the sodium salt of the monosulfated monoglyceride ofhydrogenated coconut oil fatty acids such as sodium N-methyl N-cocoyltaurate, sodium cocomonoglyceride sulfate,

ii. higher alkyl sulfates, such as sodium lauryl sulfate,

iii. higher alkyl-ether sulfates, e.g., of formulaCH₃(CH₂)_(m)CH₂(OCH₂CH₂)_(n)OSO₃X, wherein m is 6-16, e.g., 10, n is1-6, e.g., 2, 3 or 4, and X is Na or K, for example sodium laureth-2sulfate (CH₃(CH₂)₁₀CH₂(OCH₂CH₂)₂OSO₃Na).

iv. higher alkyl aryl sulfonates such as sodium dodecyl benzenesulfonate (sodium lauryl benzene sulfonate)

v. higher alkyl sulfoacetates, such as sodium lauryl sulfoacetate(dodecyl sodium sulfoacetate), higher fatty acid esters of 1,2 dihydroxypropane sulfonate, sulfocolaurate (N-2-ethyl laurate potassiumsulfoacetamide) and sodium lauryl sarcosinate.

By “higher alkyl” is meant, e.g., C₆₋₃₀ alkyl. In particularembodiments, the anionic surfactant is selected from sodium laurylsulfate and sodium ether lauryl sulfate. The anionic surfactant may bepresent in an amount which is effective, e.g., >0.01% by weight of theformulation, but not at a concentration which would be irritating to theoral tissue, e.g., <10%, and optimal concentrations depend on theparticular formulation and the particular surfactant. For example,concentrations used for a mouthwash are typically on the order of onetenth that used for a toothpaste. In one embodiment, the anionicsurfactant is present in a toothpaste at from about 0.3% to about 4.5%by weight, e.g., about 1.5%.

Nonionic surfactants include nonanionic polyoxyethylene surfactants suchas Polyoxamer 407, Steareth 30, Polysorbate 20, and PEG-40 castor oiland amphoteric surfactants such as cocamiopropyl betaine (tegobaine) andcocamidopropyl betaine lauryl glucoside condensation products ofethylene oxide with various hydrogen containing compounds that arereactive therewith and have long hydorphobic chains (e.g., aliphaticchains of about 12 to 20 carbon atoms), which condensation products(“ethoxamers”) contain hydrophilic polyoxyethylene moieties, such ascondensation products of poly (ethylene oxide) with fatty acids, fattyalcohols, fatty amides and other fatty moieties, and with propyleneoxide and polypropylene oxides (e.g., Pluronic® materials).

The compositions of the invention may optionally contain mixtures ofsurfactants, e.g., comprising anionic surfactants and other surfactantsthat may be anionic, cationic, zwitterionic or nonionic. Generally,surfactants are those which are reasonably stable throughout a wide pHrange. Surfactants are described more fully, for example, in U.S. Pat.No. 3,959,458, to Agricola et al.; U.S. Pat. No. 3,937,807, to Haefele;and U.S. Pat. No. 4,051,234, to Gieske et al., which are incorporatedherein by reference. In certain embodiments, the anionic surfactantsuseful herein include the water-soluble salts of alkyl sulfates havingabout 10 to about 18 carbon atoms in the alkyl radical and thewater-soluble salts of sulfonated monoglycerides of fatty acids havingabout 10 to about 18 carbon atoms. Sodium lauryl sulfate, sodium lauroylsarcosinate and sodium coconut monoglyceride sulfonates are examples ofanionic surfactants of this type. In a particular embodiment, thecomposition of the invention, e.g., Composition 1, et seq., comprisessodium lauryl sulfate.

The surfactant or mixtures of compatible surfactants can be present inthe compositions of the present invention in about 0.1% to about 5.0%,in another embodiment about 0.3% to about 3.0% and in another embodimentabout 0.5% to about 2.0% by weight of the total composition.

Flavoring Agents

The oral care compositions of the invention may also include a flavoringagent. Flavoring agents which are used in the practice of the presentinvention include, but are not limited to, essential oils as well asvarious flavoring aldehydes, esters, alcohols, and similar materials.Examples of the essential oils include oils of spearmint, peppermint,wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon,lemon, lime, grapefruit, and orange. Also useful are such chemicals asmenthol, carvone, and anethole. Certain embodiments employ the oils ofpeppermint and spearmint. The flavoring agent may be incorporated in theoral composition at a concentration of about 0.1 to about 5% by weightand about 0.5 to about 1.5 weight %. The dosage of flavoring agent inthe individual oral care composition dosage (i.e., a single dose) may beabout 0.001 to 0.05 weight % and in another embodiment about 0.005 toabout 0.015 weight %.

Other Optional Ingredients

In addition to the above-described components, the embodiments of thisinvention can contain a variety of optional dentifrice ingredients someof which are described below. Optional ingredients include, for example,but are not limited to, adhesives, sudsing agents, sweetening agents,and additional coloring agents. These and other optional components arefurther described in U.S. Pat. No. 5,004,597, to Majeti; U.S. Pat. No.3,959,458 to Agricola et al. and U.S. Pat. No. 3,937,807, to Haefele,all being incorporated herein by reference.

Process for the Preparation of the Composition

In a further aspect, the present invention provides a process for thepreparation of a composition as defined in any preceding claim, theprocess comprising:

-   -   i) admixing an amount of silica particles in water with an        amount of a base, the base comprising a metal ion, to produce        the core shell silica particles, wherein each core shell silica        particle comprises a silica core, and a surface of the silica        core is etched with metal silicate;    -   ii) admixing the core shell silica particles formed in step i)        with an orally acceptable carrier vehicle comprising a        non-aqueous solvent, a dye having a blue to blue-violet color        with a hue angle in the CIELAB system ranging from 200 to 320        degree, and an amount of water to produce a composition        comprising from 3 weight % to 30 weight % water.

Step i) of the invention may comprise admixing an amount of SiO₂particles in water with an amount of NaOH in solid or aqueous form, withor without a humectant, to produce the core shell silica particle.Sodium hydroxide reacts with the surface of the SiO₂ particle to etch ashell of layers(s) of Na₂SiO₃ as follows:SiO₂+2NaOH→Na₂SiO₃+H₂O

As can be seen from the reaction scheme, no NaOH will result in nochange to the silica, whereas at the other extreme, complete reactionwith 2 moles of NaOH per 1 mole of silica will result in the completeconversion into Na₂SiO₃. In order, to obtain the core shell particles ofthe invention, the reaction process must be controlled so as to notachieve complete conversion into Na₂SiO₃.

The process for making the core shell silica particles comprises ofetching the original silica in order to form Na₂SiO₃ layers, i.e. theNa₂SiO₃ layers are not additional layers coated on top of the surface ofthe silica.

As the covalent bonds of the SiO₂ network are turned into ionic bondsbetween Na⁺ and SiO₃ ²⁻, the surface becomes polarized and adsorbs waterand the humectant to produce the core shell silica particle.

The process may comprise a further step after step i) and prior to stepii) of reacting the core shell silica particles formed in step i) with ametal salt comprising a second metal ion to form core shell silicaparticles comprising silicate of the second metal ion on a surface ofthe silica core.

The base may be in solid or aqueous form. The base is preferablyselected from the group consisting of sodium hydroxide, potassiumhydroxide, calcium hydroxide, barium hydroxide, ammonium hydroxide,sodium carbonate, potassium carbonate, trisodium phosphate, disodiumphosphate, potassium phosphate, dipotassium phosphate, tetrasodiumpyrophosphate, and tetrapotassium pyrophosphate. A particularlypreferred base is sodium hydroxide, most preferably 50% aqueous sodiumhydroxide solution.

Step i) may be carried out at a temperature in the range of from 17° C.to 90° C. In one embodiment the process is carried out at roomtemperature, i.e. 20 to 26° C. In another embodiment step i) is carriedout at a temperature of from 70 to 90° C. When preparing the core shellsilica particles on an industrial scale, the mixer used to mix thereactants, such as a Lee mixer (Lee Industries), is preferably notheated up.

In one embodiment, in step i) the base is sodium hydroxide and theprocess is carried out at a temperature of from 70 to 90° C. In anotherembodiment, in step i) the base is potassium hydroxide and the processis carried out at room temperature. This is embodiment is advantageousbecause the use of the more reactive potassium hydroxide means thatheating is not required.

The formation of the core shell silica particles in step i) is typicallycomplete after a time period of 2 hrs.

The weight ratio of the amount of base to the amount of silica particlesin step i) may be from 1:1 to 1:20. The weight ratio for the amount ofbase to the amount of silica particles may be from 1:1 to 1:3.

The turbidity of the core shell silica particles is decreased byincreasing the weight ratio for the amount of base to the amount ofsilica particles.

An average depth of from 1 to 15 nm of silica may be removed from thesurface of the silica particle to form the silica core, and metalsilicate is formed on top of the silica core in step i). The averagedepth of silica removed typically increases as the weight ratio for theamount of base to the amount of silica particles increases. The d(0.5)of the silica core may be from 1 to 15 nm less than the d(0.5) of thesilica particles of the starting material. The d(0.5) of the silica coremay be about 2 nm less than the d(0.5) of the silica particles of thestarting material. The d(0.5) particle diameter of the silica core maybe about 6 nm less than the d(0.5) of the silica particles of thestarting material. There is a greater percentage reduction in particlediameter for rigid silica particles such as fumed silica than for poroussilica particles such as high cleaning silica. For example, for fumedsilica the percentage reduction in particle diameter (d(0.5)) may beapproximately 15%, whilst for porous high cleaning silica the percentagereduction in particle diameter (d(0.5)) may be approximately 0.06%.

The formation of the core shell silica particles of the inventiondescribed above can be effected by manipulating the amount of basedused, the amount of humectant used, the amount of metal salt used, andvarying the temperature of the reaction.

The formation of the core shell particles can be monitored bydetermining the pH of the reaction mixture. In one embodiment, step i)is complete when the pH of the reaction mixture decreases by at least0.5 pH units from the initial mixture of reactants. In anotherembodiment, step i) is complete when the pH of the reaction mixturedecreases by at least 0.8 pH units from the initial mixture ofreactants. Typically, step i) is complete when the pH of the reactionmixture is about 11. The process may comprise a further step after thestep of forming the core shell particles of adjusting the pH of thereaction mixture to from 7 to 8. The pH of the reaction mixture istypically adjusted using acid. The acid may be selected from the groupconsisting of phosphoric acid, citric acid and lactic acid.

The formation of the core shell particles in step i) can also bemonitored by determining the conductivity of the reaction mixture. Theend point of the process results when the conductivity of the reactionmixture decreases by at least 250 micro Siemens/cm (μS/cm) because theelectric charges transfer from highly mobile ions (NaOH) to much lessmobile silica surface (mobility≈0). In yet another embodiment, the endpoint of the process results when the conductivity of the reactionmixture decreases by 250-400 μS/cm. Typically, the core shell silicaparticles are formed when the conductivity of the reaction mixturedecreases by at least 2 milliSiemens/cm (mS/cm). Usually, the core shellsilica particles are formed when the conductivity of the reactionmixture decreases by at least 5 mS/cm.

In an embodiment, the core shell silica particles of the invention areformed when at least 1-6% of each of the silica particle startingmaterial has been etched with one or more layers of silicate. In anotherembodiment, the core shell silica particles of the invention are formedwhen at least 2.5-5% of each of the silica particle starting materialhas been etched with one or more layers of Na₂SiO₃. In anotherembodiment, the core shell silica particles of the invention are formedwhen at least 3.5-4% of each of the silica particle starting materialhas been etched with one or more layers of silicate.

It is understood that while general attributes of each of the abovecategories of materials may differ, there may be some common attributesand any given material may serve multiple purposes within two or more ofsuch categories of materials. All of the ingredients in the compositionsmay have functions in addition to their primary function, and maycontribute to the overall properties of the composition, including itsstability, efficacy, consistency, mouthfeel, taste, odor and so forth.Preferably, the carrier is selected for compatibility with otheringredients of the composition.

As used throughout, ranges are used as shorthand for describing each andevery value that is within the range. Any value within the range can beselected as the terminus of the range. In addition, all references citedherein are hereby incorporated by referenced in their entireties. In theevent of a conflict in a definition in the present disclosure and thatof a cited reference, the present disclosure controls.

Unless otherwise specified, all percentages and amounts expressed hereinand elsewhere in the specification should be understood to refer topercentages by weight based on the total weight of the composition. Theamounts given are based on the active weight of the material. Forconvenience, components of the composition of invention are expressed inthe singular; however it is to be understood that mixtures of componentsare encompassed by use of the singular expression, for example, “anorally acceptable carrier polymer” may include mixtures of two or morepolymers described herein.

The invention also includes a method for whitening teeth comprisingadministering the composition of the invention to the oral cavity of asubject in need thereof. In one embodiment of the invention, the methodprovides a teeth whitening effect of at least a 20% increase in toothsurface whiteness which lasts for up to four hours.

Embodiments of the present invention are further described in thefollowing examples. The examples are merely illustrative and do not inany way limit the scope of the invention as described and claimed.

EXAMPLES Example 1

It has been found that when the carrier system for a blue dye isprimarily non-aqueous the ability of the blue dye to increase thewhiteness of teeth is enhanced. We have shown the increase in toothwhiteness is greater when blue dye is formulated into a non-aqueoussolution of glycerin as compared to when the blue dye is delivered froman aqueous solution.

TABLE 1 Δb* ΔWIO Dye control in AQ −0.9 3.9 Dye control in non- −2.711.7 AO

In addition, bioadhesive materials such as VM/MA Copolymer (Gantrez) andcross-linked PVP have been demonstrated to increase blue dye retentionon teeth. The inventors have surprisingly found that when the surfacechemistry of silica is modified with a strong base the resultingparticle can also increase the retention of blue dye on the surface.This novel material consisting of a silica core etched with silicate isreferred to as core shell silica (CSS).

TABLE 2 Non-AQ Δb* after ΔWIO after Solution Δb* initial ΔWIO initial 30min soak 30 min soak Dye −2.7 5.5 0.4 −1.6 Control Dye + −3.2 13.7 −0.54.1 Gantrez Dye + −2.5 11.0 −0.8 5.1 Coreshell Silica

The above experiments found that CSS was more effective than a Gantrezcontaining solution of dye in glycerin in the delivery and retention ofblue dye to teeth for an increase in tooth whitening. In addition tosimple solutions, we have found CSS can be extremely effective atmaintaining increased in tooth whitening when delivered from adentifrice formula having a critical level of water.

Example 2

Experimental Method for Evaluating Retention of Blue Dye on Teeth andResulting Tooth Whiteness

The roots of human third molars were removed and the tooth was bisectedfrom the crown through the root. Each half of the tooth was mounted inmethacrylate resin and then secured in a brushing tray, enamel sidefacing out, using a thermal impression compound. Four teeth were mountedper tray. The teeth were brushed for 10 minutes with a 1:2 (w/w) silicatoothpaste slurry to remove any extrinsic surface stains, rinsed withdeionized water, dried with cool air, and baseline CieLab measurementswere recorded with a spectrophotometer (Spectroshade Micro, MHTtechnologies). Teeth were submerged in saliva (9 mL/tray), aged at 37°C. with gentle agitation for 15 minutes. The test toothpaste (6 g) wasthen added to the tray already containing 9 mL saliva, the teeth werebrushed for 2 minutes, rinsed with 100 mL deionized water, dried withcool air, and CieLab measurements were recorded. The teeth were aged insaliva for 10 minutes or 30 minutes. Teeth were rinsed and dried withcool air before CieLab measurements were recorded at each time-pointduring the soaking cycle. Δb* is reported and is the change in theyellow-blue axis in CieLab color space. This is the metric by which thedeposition of blue dye can be quantified. The Ab* reported is thedifference between the b* values of the tooth after surface stains areremoved to that after brushing with the product containing blue dye. Achange in a whiteness index (WIO) is also be reported to show that thedeposition of blue dye results in an increase in the whiteness of atooth.

TABLE 3 Formula composition with ranges Ingredient Target Weight %Weight % Range Glycerin 58.86 High Cleaning Silica 20 10-25 Water 7 3-30 Thickening Silica 4 0-6 Polyethylene Glycol 3 Sodium LaurylSulfate 1.5 Coreshell Silica 2 1.5-5  Titanium dioxide 0.5 SodiumSaccharin 0.5 Xanthum Gum 0.3 Sodium Carboxymethylcellulose 0.25 0.1Sodium Fluoride 0.24 FD&C Blue#1 0.05 0.02-2  

Core shell Silica and blue dye vs. matching formula without core shellsilica. Both formulas contain 7% water and 0.05% FD&C blue #1 dye.

TABLE 4 Δb* ΔWIO 10 min 30 min 10 min 30 min Initial saliva salivaInitial saliva saliva 0% CSS −1.3 0.0 0.4 7.04 3.33 1.75 2% CSS −1.4−0.6 −0.3 5.95 4.71 3.34

The data in table 4 demonstrate that the addition of CSS to the formularesults in similar deposition of blue dye but an increase in theretention time of the dye on teeth.

TABLE 5 CSS vs. Gantrez Δb* ΔWIO 10 min 30 min 10 min 30 min Initialsaliva saliva Initial saliva saliva 2% CSS −1.4 −0.6 0.3 5.95 4.71 3.342% Gantrez −0.8 −0.1 −0.2 4.95 2.92 2.61

At 2% loading in low water (7%) dentifrice, CSS provides superior bluedye delivery and retention to Gantrez.

TABLE 6 2% xPVP with 0.05%, 0.10% and 0.15% FD&C Blue #1 Δb* ΔWIOInitial Initial 0.05% FD&C Blue #1 −1.4 6.0 0.10% FD&C Blue #1 −2.5 7.80.15% FD&C Blue #1 −2.5 9.9

It can be seen from the data in Table 6 that 2% core shell silicaprovides a dose response in whitening efficacy with various levels ofblue dye.

In a dentifrice formula having low water (approximately 7%) and CSS,increasing the amount of blue dye will increase the amount of dyedeposited on teeth and the perceived whiteness of the teeth. At only0.05% FD&C blue number one there is a significant change in toothwhiteness from the deposition of blue dye.

In summary, we have shown that a low water formula containing CSS canimprove the retention of blue dye on teeth. For optimal blue dyedelivery a minimal amount of water to activate the CSS is required.

As those skilled in the art will appreciate, numerous changes andmodifications may be made to the embodiments described herein withoutdeparting from the spirit of the invention. It is intended that all suchvariations fall within the scope of the appended claims.

What is claimed is:
 1. A tooth whitening oral care compositioncomprising: (i) a dye having a blue to blue-violet color with a hueangle in the CIELAB system ranging from 200 to 320 degrees; (ii) coreshell silica particles, wherein each core shell silica particlecomprises a silica core, and a surface of the silica core is etched withmetal silicate; (iii) an orally acceptable carrier vehicle comprising anon-aqueous solvent; and wherein the composition comprises water in anamount of from 3 weight % to 30 weight %.
 2. The composition accordingto claim 1, wherein the metal silicate for each core shell silicaparticle is: i) a metal silicate of a monovalent metal ion; or ii) ametal silicate of a monovalent metal ion and one or more of a of adivalent metal ion, a trivalent metal ion, and a tetravalent metal ion.3. The composition according to claim 2, wherein the monovalent metalion is a group I metal ion.
 4. The composition according to claim 1,wherein the metal silicate comprises the formula M¹ ₂SiO3.x H₂O, whereinM¹ is a monovalent metal ion, optionally a group I metal, and x is from0 to 10; and the outer 10 nm depth of a core shell silica particlecomprises from 0.1 to 10 weight % M¹ ₂SiO3.xH₂O.
 5. The compositionaccording to claim 1, wherein the outer 10 nm depth of a core shellsilica particle has the general formula:(SiO₂)_(p)[O_(o)*N⁺ _(n)H⁺ _(h)OH⁻ _(j))].qH₂O wherein O* is oxygen inthe silicate form; N is a group I metal ion; p, o, n, h, j and q are theatomic percentages of each component; and the total charge of each coreshell silica particle is zero.
 6. The composition according to claim 1,wherein the metal silicate comprises a silicate of a group 2 metal ion,a transition metal ion, a group 13 metal ion, a group 14 metal ion ormixtures thereof.
 7. The composition according to claim 1, wherein themetal silicate comprises the formula M²SiO3.x H₂O, wherein M² is adivalent metal ion selected from the group consisting of Zn, Ca, Mg, Sn,and Sr, and x is from 0 to
 10. 8. The composition according to claim 6,wherein the outer 10 nm depth of each particle has the general formula:(SiO₂)_(p)[O*_(o)N⁺ _(n)M²⁺ _(m)U³⁺ _(u)V⁴⁺ _(v)H⁺ _(h)OH⁻ _(j) ].qH₂Owherein O* is oxygen in the silicate form; N is a monovalent metal ion;M is a divalent metal ion; U is a trivalent metal ion; V is atetravalent metal ion; p, o, n, m, u, v, h, j and q are the atomicpercentages of each component; and the total charge of each core shellsilica particle is zero.
 9. The composition according to claim 1,wherein the d(0.5) value of the core shell silica particles ranges from5 nm to 50 μm.
 10. The composition of claim 1, wherein the amount ofcore shell silica particles is 0.001 to 10 weight % of the composition.11. The composition of claim 1, wherein the dye comprises from 0.001 to2 weight % of the composition.
 12. The composition according to claim 1,wherein the dye comprises a metal ion.